Of course, Nakamura decides to play on, instead of repeating moves with 23...Ra8.
21. a2b1  21... b6b5 Preparing Nb6-a4. Black already has a considerable positional advantage. 22. h2h3  22... a8d8  23. b1a2 Not the best square for the queen, but maybe Nepomniachtchi was counting on a draw by move repetition.